Researchers now say that could mean salmon caught anywhere off North America's Pacific coasts could be affected, though the health effects aren't generally serious. The scientists, however, warn the problem could spread if not remedied: Because salmon is often packed and transported on ice (but not frozen), the tapeworm's larvae may be able to survive the trip, possibly infecting consumers in Europe, New Zealand, China, and other parts of the US.

The researchers cut open 64 wild Alaskan salmon in 2013 to find the larvae (some up to 15 mm long), and gene sequencing identified it as the Japanese tapeworm. Four species are known to carry it: chum salmon, masu salmon, pink salmon, and sockeye salmon.

Per Food Safety Magazine, infection risk is increased when consuming raw or undercooked fish. A preventive medicine professor at Vanderbilt University School of Medicine tells CNN most infected humans remain asymptomatic — some may feel slight abdominal discomfort or nausea — though there are rare cases in which the infection can turn serious. The CDC notes that freezing or cooking the fish will annihilate Diphyllobothrium parasites.